Typically, lamellar structured liquid cleansing compositions (e.g., shower gel compositions) comprise a mixture of anionic surfactants (for cleansing and foaming attributes) and mild surfactant. In a typical shower formulation, the mild surfactant may be an amphoteric and/or zwifterionic surfactant such as those described in U.S. Ser. No. 08/512,010 mentioned above, hereby incorporated by reference into the subject application.
In such lamellar structured compositions, however, it has been found that there is considerable thinning of product as the product is cooled down to temperatures of 20.degree. to 0.degree. F. This loss of viscosity is not a desirable property.
Unexpectedly, applicants have found that when alkalimetal alkyl amphoacetate is used as greater than 25% to 90%, preferably 30% to 90% and more preferably about 40% to 90% of the amphoteric and/or zwitterionic component in the surfactant system, there is a significant increase in product stability.
U.S. Ser. No. 08/512,010 shows one example (Example IX at page 23) where sodium cocoamphoacetate is used. However, in neither that example or in the other eight examples are there ever taught blends of other amphoteric (e.g., betaine) and amphoacetate. Nor is there any teaching or suggestion in that application that blends of amphoteric will ameliorate low temperature instability in such compositions. Indeed, until the problem of low temperature instability was even appreciated, it could not have been known that selecting the specific surfactant system of the invention could ameliorate the problem.